Implantable medical devices (IMDs) can be implanted into patients for various purposes, such as heart rhythm management and stimulation. Some examples of these devices include cardiac function management (CFM) or cardiac rhythm management (CRM) devices such as implantable pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization devices, and devices that include a combination of such capabilities. CFM IMDs, for example, can monitor for cardiac arrhythmia, and administer therapy in response.
IMDs can communicate wirelessly with an external device. Examples of the external device can include an IMD programmer that provides bi-directional communication between the IMD and the caregiver, a patient activator that calls a patient to activate an implantable device, or a patient data display that reads and displays information from the IMD.